Heater for asphalt concrete roadways and the like

ABSTRACT

Disclosed herein is an embodiment of a heater for asphalt concrete repaving apparatus which utilizes fuel, such as pentane, to direct a flame onto a radiant heating element. The flame is redirected radially outwardly along the radiant heating element so the flame will not impinge on the road surface and only radiant heat is used. Such radiant heat will penetrate the road surface to a depth of 1 inch or more in a relatively short period of time whereupon the heated and softened asphalt together with portions thereof beneath the heated portion are excavated. Additional heat is applied to the excavated material to further soften it and small quantities of new asphalt material may be added if desired before the reworked material is again laid to form a road surface.

United States Patent [191 Cutler Apr. 2, 1974 [54] HEATER FOR ASPHALTCONCRETE 3,055,280 9/1962 Neville .L 404/95 ROADWAYS AND THE LIKE3,221,617 12/1965 Quigg 404/95 3,096,696 7/1963 Reisser 404/95 [75]Inventor: Earl F. Cutler, Lawrence, Kans. 3 372, 2 3 1968 Smarzak 404/95Assigneez Cutler p g Associates, 2,705,906 4/1955 Fizzell 404/95Incorporated Lawrence Primary ExaminerNi1e C. Byers, Jr. [22] Filed:Aug. 18, 1972 Attorney, Agent, or Firm--Olson, Trexler, Wolters, [211App. No: 282,005 Bushnell & Fosse, Ltd.

Related US. Application Data [57] ABSTRACT [63] of 129,404 MarchDisclosed herein is an embodiment of a heater for as- ]971 phaltconcrete repaving apparatus which utilizes fuel,

such as pentane, to direct a flame onto a radiant heatg% 404/95 65: 23ing element. The flame is redirected radially out- 1 I} c wardly alongthe radiant heating element so the flame [58] Field of Search 404/95,77; 239/169, 521,

239 126 271 1 271 2 271 3 3 3 39() W11] not impinge on the road surfaceand only radiant l 4 heat is used. Such radiant heat will penetrate theroad I surface to a depth of 1 inch or more in a relatively short periodof time whereupon the heated and soft- [56] References Cted ened asphalttogether with portions thereof beneath UNITED STATES PATENTS the heatedportion are excavated. Additional heat is 3,021,893 2/1962 Honger431/329 applied to the excavated material to further soften it 3,067,81162 st r... 43 X and small quantities of new asphalt material may be1199568 8/1965 Baumannk 431/328 X added if desired before the reworkedmaterial is again 3,199,572 8/1965 B0u1et.... 431/329 laid to form aroad u 3,322,179 5/1967 Goodell 431/329 X 1,984,849 12/1934 Van Allen404/95 X 2l Claims, 10 Drawing Figures PATENTEDAFR 2 1974 I 3.801212 sawu or 5 PATENTEDAPR 21914 3,801,212

SHEET 5 BF 5 'FIG.9

us I us HEATER FOR ASPHALT CONCRETE ROADWAYS AND THE LIKE REFERENCE TORELATED APPLICATION This is a continuation-in-part of my earlier filedcopending application Ser. No. 129,404 filed Mar. 30, 1971, now U.S.Pat. No. 3,724,445.

BACKGROUND OF THE INVENTION This invention relates generally to roadwayresurfacing apparatus, and more particularly to heating units utilizedas one or more work stations in such roadway resurfacing apparatus.

This invention deals with substantial improvements in my earlier filedcopending application Ser. No. 129,404filed Mar. 30, 1971 and the entiresubject matter of this earlier application is included herein byreference. Road surfacing apparatus as set forth in my US. Pat. No.3,361,042 provides means for quickly and inexpensively resurfacingroadways made of asphalt concrete materials, or the like. The apparatusmay be eightto 12 feet wide and 40 to 50 feet long and moved along theroadway in a slow rate so that during a single continuous pass over thepavement, the old road surface in front of the machine is excavated andconverted to a refinished road surface at the rear of the machine. Adistinct advantage of repaving apparatus of this type is that thefinished repaved strip of roadway is immediately freely available forvehicular traffic within a matter of minutes after completion.

The heater apparatus of this invention is advantageously utilized inroad repaving machinery which performs the following functions duringthe repaving process. First the road surface is heated in a nonoxidizingenvironment consisting substantially of all radiant heat so that heatpenetration is obtained to a depth of 1 inch or so below the surface.This is followed by scarifying deeply to excavate and disarrange thematerial heated by the first step. Then piling the disarranged materialfor maximum surface exposure so it can be further heated, this heatbeing substantially entirely of radiant heat as in the first instance.Then if needed adding very minor amounts of conventional tack coat tohelp weld the total hot top mixture to the substraight from which theheated material was removed. This is followed by tamping and screedingwhich, in turn, is followed by compacting as by conventional rollingmeans.

The heater apparatus may also be used as an attachment to a tractor orthe like especially where it is desired to heat relatively small areasof a roadway for patches or other repairs.

Heretofore, heating of the road surface was accomplished in a flamewhich produced a nonoxidizing atmosphere so that the temperature of theroad surface could be elevated higher than the material could experiencein air without being set on fire. This was needed for maximum heatpenetration of the road surface. However, to achieve this hightemperature and penetration of the road surface, the amount of fuelrequired was substantial.

SUMMARY OF THE INVENTION apparatus for road repaving machinery whichprovides substantially one hundred percent radiant heat which will raisethe temperature of the road surface to about 300F to a penetration depthof about 1 inch or more.

Briefly, the heating apparatus of this invention may form two or morestations of the road repaving machine and each heating apparatuspreferably is of the same structural arrangement. Therefore, onlydetails of a single heating apparatus will be set forth in greatparticularity. The heating apparatus is provided with a fuel receivingmanifold which ispositioned over a heating chamber and is rectangular inconfiguration like the heating chamberIA plurality of discrete fuelburning elements have conduit portions extending through the heatingchamber and into the manifold chamber to receive a mixture of hot gasand air which is a combustible mixture that is burned at the heatingnozzle. To achieve the proper pressure and flow of fuel and air mixture,a variable quantity air blower is in fluid communication with themanifold chamber so that deliveryv combustion process. Therefore, thepressure within the heating chamber can be maintained substantiallyequal to that of the atmospheric pressure outside the chamber and littleor no heat will escape from under the side walls thereof. Also, bymaintaining the pressure within the heating chamber substantially equalto the outside pressure, minimum air is drawn into the heating chamberfrom around the peripheral lower edges thereof and minimum oxidation oractual combustion on the road surface is the result.

In accordance with the principles of this invention the flame from theheating apparatus is directed downwardly and then deflected laterally orradially outwardly so as to fall across substantially the entire area ofa radiant heating element which converts the heat from the flame toradiant heat. The radiant heating element is positioned adjacent theroad surface and thereby provides red and infrared heat energy topenetrate the road surface to depths of 1 inch or more, this beingaccomplished in a relatively short period of time and with the use of aminimum of fuel.

Many other objects, features and advantages of this invention will bemore fully realized and understood from the following detaileddescription when taken in conjunction with the accompanying drawingswherein like reference numerals throughout the various views of thedrawings are intended to designate similar elements or components.

Brief Description of the Drawings FIG. 1 is a side elevational view of aroadbed resurfacing apparatus utilizing the heater structure of thisinvention;

'FIG. 2 is a perspective fragmentary view of a heater structure which isconstructed in accordance with this invention;

FIG. 3 is a side elevational sectional view of the heater structure ofFIG. 2;

FIG. 4 illustrates an air control mechanism for controlling the volumeof air delivered to an air fuel mixing chamber of the heater structureof this invention;

FIG. 5 is an enlarged fragmentary view showing a dis crete heater unitmounted within the heater structure of this invention;

FlG. 6 shows an alternate flame detectorarrangement which can be used inthe heater unit of FIG. 5;

FIG. 7 is a top view of the heater arrangement of FIG. 3 showing theplacement of the discrete heater units and the associated radiantheating elements together with the air blower and manifold structurepositioned above the heater chamber;

FIG. 8 is a plan view of an alternate form of manifold construction usedin the heater apparatus of this invention;

Detailed Description of the Illustrated Embodiment Referring now to FIG.1 there is seen a side view of a road resurfacing equipment and isdesignated generally by reference numeral 10. The road resurfacingequipment It) utilizes a plurality of large. pneumatic wheels 13 havingsufficient contactsurface area so that the weight of the machine isdistributed uniformly. As the road resurfacing equipment moves forwardover a damaged road surface, the front end of the machine will heat anddig up the road surface to a depth of approximately oneto two inchesmore or less. The quantity of old road surface now forming loosepavement is additionally heated so that it becomes substantiallycompressible under the weight of roller action. Additional quantities ofasphalt material may be supplied, as desired, to build up the roadsurface to the previous height or to a height greater than the old roadsurface. The rate of travel of the machine may be in theqorder of eightto 25 feet per minute thereby providing a complete reconstructed roadsurface upon which vehicular traffic can commence substantiallyimmediately after the new road surface has been formed.

16 into a hopper or receptacle 17 at the front end of the machine. Aconveyor 18 along the top portion of the frame transports the newmaterial from the hopper to one or more various work stations. A controlstation 19 is located intermediate the machine and an operator isstationed there to control the direction of travel as well as the rateof travel'of the machine. Also, the operator at the control station 19controls various functions such as the amount of heat supplied to theroad surface by the various burners. One or more diesel engines 20 aremounted at the rear portion of the machine and include various controlpanels 20a which operate hydraulic pumps or compressors. The wheels 13are motorized by independent hydraulic motors operated by hydrostatichydraulic supply pump control mechanisms. A plurality of fuel tanks 21are mounted on top of the support frame 22 of the machine and are usedto carry fuel A quantity of new material 14 is delivered via a trucksupplies for both the diesel engine '20 and for the burners 24 and 26.One or more of the fuel tanks 21 may be filled with diesel fuel whileone or more of the fuel tanks may be filled with pentane fuel foroperating the burners. The pair of road surface heaters 24 and 26 arespaced sufficiently apart so that the heated road surface can be dug upand rearranged for additional heating of the dislodged components of theroad. The manner in which the road resurfacing apparatus 10 operates ismore fully discussed in my US. Pat. No. 3,361,042 and no furtherdetailed description of operation is deemed necessary herein.

The road resurfacing apparatus 10 includes a pair of heaters 24 and 26each constructed substantially in the same manner and therefore only asingle heater will be discussed in detail. The heater 24 includes a heatchamber 28 facing downwardly to be positioned immediately over the roadsurface to be repaved so that the road surface can be heated to a depthof approximately one inch or more thereby softening the material formingthe old road surface. After heating of the road surface 'it is excavatedby scarifying or the like with a plurality of cutting points or knivesand additional heat is supplied by the second burner 26.

The heating chamber 28 is formed by a plurality of chamber-forming walls30 of fabricated construction and a top wall or roof 31. The bottom ofthe chamber is open and the downwardly extending peripheral edgeportions of the side walls are closely spaced to the road surface sothat minimum air gap is obtained. the pressure within the heatingchamber 28 is maintained substantially equal to the atmospheric pressureoutside of the chamber so that no heat escapes from the space betweenthe walls and the road surface, and similarly, no

unwanted oxidizing air will be drawn into the heating chamber from theoutside atmosphere.

Positioned above the heating chamber 28 is a fuel mixing chamber 32which, in turn, is in fluid communication with a pressure blower unit33. The pressure blower unit 33 supplies a quantity of air, under slightpressure so that the air fuel mixture is directed toward a plurality ofburners within the heating chamber 28. While the pressure provided bythe plower 33 is relatively low, the air volume moved by the blower ismaintained relatively high for maximum heating of the bumers. The airfuel mixture supplied from the fuel mixing chamber 32 is then directedinto a distributing manifold 34 mounted on top of the heating chamber28. The air fuel manifold 34 preferably takes the form of a rectangularchamber having a common wall between the heating chamber and themanifold. A plurality of upwardly extending large diameter exhauststacks 36 are located at each of the four corners of the burner so thatheat formed within the heating chamber 28 can rise through the exhauststacks and be expelled at a level substantially above street level sothat workmen about the machine are not subjected to the extreme heat.

Referring now to FIG. 2 a detailed fragmentary perspective view of theheater 24 is illustrated, it being understood that the side of theheater 24 is typical with respect to the other side of the heater. Theside walls 30 include a plurality of reinforcing members 37 positionedvertically about the side walls. A top and bottom edge 38 also formreinforcing members about the side walls. The manifold 34 is in fluidcommunication with an enlarged manifold portion 340 which-forms the topwall of the heating chamber. The manifold portion 340 can be formedeither as an integral part of the heating chamber as shown, i.e. formedby the top wall thereof, or it can be formed as a separate unit mountedon top of the heating chamber. The fuel mixing chamber 32 includes a top40 which has a flange 41 fastened thereto for supporting the blower 33.The blower 33 has the output portion thereof 33a in direct fluidcommunication with a manually adjustable flow control valve 42. The flowcontrol valve 42 is adjustable to select the proper volume of airdirected to the manifold 34.

To insure that the air fuel mixture directed to the burners within theheat chamber 28 is expanded to the maximum extent, an air heat pipe 43is in fluid communication between one of the exhaust stacks 36 and theoutlet port 33a of the blower 33. In the illustrated embodiment theconnection to the outlet 33a is made below the flow control valve 42, itbeing understood that this hot air connection can be made above the flowcontrol valve, if desired. A fuel line 44 is connected to the fuelmixing chamber 32 and therein the fuel, preferably pentane or the like,is admixed with the air from the blower 33 and delivered to the firstmanifold portion 34 and therefrom to the second manifold 34a. The fueldelivered through the line 44 is heated by a preheater unit, to bedescribed hereinbelow, which is mounted within the heating chamber 28.Therefore, fuel from the tanks 21 is supplied to the inlet line 44a anddirected through the preheater unit and therefrom to the fuel line 44and into the mixing chamber 32. By so preheating the fuel and heating aportion of the air supplied to the mixing chamber, maximum expansion ofthe air fuel mixture is obtained before combustion. This enables the airfuel mixture to ignite with minimum expansion of gases so that little orno pressure is obtained within the heating chamber.

Referring now to FIG. 3 there is seen a side elevational sectional viewshowing more clearly the details of construction of the burner of thisinvention. Here it can be seen that the mixing chamber 32 is in opencommunication with the manifold 34 by means of a large opening 46through the top wall of the manifold. I-Iowever, it will be understoodthat the top wall of the manifold can be provided with a plurality ofsmall holes rather than the large opening 46. Similarly, the top wall ofthe manifold portion 34a is provided with an opening 47 to receive thequantity of air fuel mixture from the manifold 34. Similarly, this largeopening 47 can be replaced by a top wall portion having a plurality ofsmall holes formed therein. The air fuel mixture from the chamber 32 isillustrated by the plurality of arrowed lines directed through themanifold.

The bottom wall of the manifold portion 34a is provided with a pluralityof threaded members 38, they being nut-like units or the like secured,as for example by welding, to the inner wall portion of the manifold.The threaded units 48 receive burner units 49 therein, the burners beingdirected downwardly toward the pavement to be heated. Each of the burnerunits 49 includes a radiant heat element 50 upon which the open flame ofthe burner is impinged so that the flame heat produced by the burner isconverted to radiant heat. The radiant heating elements 50 causethepavement to be heated to a depth of approximately 1 inch or more,this being indicated by the portion 52 of the pavement shown in FIG. 3.Preferably, the radiant heating elements 50 are formed of screen-likemembers of Inconel material which is a nickel-based,heat-and-oxidizationresistant material having approximately 13 percentchromium, 6 percent iron and small amounts of manganese, silicon andcopper. It will be understood that other similar radiant heatingmaterial may be utilized if desired.

Also mounted within the heating chamber 28 is a preheater unit 53, whichas mentioned above, has a fuel input line 44a connected to one portionthereof and the fuel output line 44 connected to the fuel mixing chamber32. The preheater unit 53 substantially increases the temperature of thefuel before it is delivered to the mixer chamber 32 so that maximumexpansion of the fuel is obtained before combustion thereof.

Referring now to FIG. 4 there is seen a detailed sectional view of theair flow control valve 42 which is connected in the output portion 33aof the blower 33. The air flow control valve 42 includes a fixed flangeportion 56 formed on the rectangular conduit section 57. A plurality ofholes 58 are formed near the periphery of a portion of the flange 56 toreceive a pin 59 secured to an extended handle portion 60. The handle isused to rotate a vein element 61 so that a port 62 therethrough ispositioned either in line or transverse to the flow path through theconduit section 57. The hot air inlet 43 is positioned below theadjustable vein 61 and admits a quantity of heated exhaust air from oneof the vertical exhaust stacks 36, FIG. 2. While a cross vein type ofair flow control device is shown herein, it will be understood that anysuitable air flow control mechanism can be used in its place.

Referring now to FIG; 5 there is seen an elevational sectional view ofone of the burner units 49 which is mounted within the heating chamber28. Here it canbe seen that the threaded fastener 48 has a meteringorifice 69 substantially in alignment with the opening through a pipe70. Air fuel mixture within the manifold 34a is delivered through themetering orifice 69 and the pipe 70 to enlarged chamber'portion of acylinder 72. Within the cylinder 72 is mounted a baffle element 73 whichhas an enlarged aperture 74 centrally thereof. The baffle 73 servesfurther to agitate and mix the air fuel mixture before it is deliveredto the lower burning portion of the cylinder 72 wherethe air fuelmixture is ignited. Secured to the bottom peripheral portion of thecylinder 72 are a plurality of support plates 76 having upwardly turnedend portions 77a and radially outwardly turned bottom portions 77b forsecuring to the cylinder and radiant heating element 50, respectively.The support legs 76 are secured by nut and bolt fasteners 78, which mayinclude suitable washer elements as desired. The flame from the cylinder72 is directed toward a deflector element 80 which has a curved surfaceexposed to the flame so that the flame is directed radially outwardlyacross the radiant heating element 50 to more efficiently heat the same.The deflector element 80 is mounted to the screen by means of a bolt 81and nut 82.

The deflector element 80 may take several different configurations tocause the flame to be directed radially outwardly over the screenelement. For example, FIG. 6 shows an alternate form of a deflectorelement which is designated generally by reference numeral 800. Thedeflector element 80a, in this instance, is mounted below the radiantheating element 50 so that the aperture thereof is in close proximity tothe nut 82 rather than the head of the bolt 81.

FIG. 7 illustrates the orientation of the various radiant heatingelements 50, they being substantially square in configuration andarranged diagonally within the heating chamber 28, this being shown inthe broken away portion of the drawing of FIG. 7. This type ofconfiguration insures that maximum radiant heating is directed towardthe pavement beneath the same. Also shown in FIG. 7 is the detail of thepreheater unit 53,

it being formed of a plurality of windings of tubular material whichsupplies the fuel to the mixing chamber 32. The coils of the tubularmaterial may be wrapped about a ceramic support member 90 which, inturn, is bolted in place under the heating chamber. FIG. 7 also showsthat one heating element may be provided with a pair of manifoldsections 34 and blowers 33. The second manifold and blower element unitsare designated with a prime adjacent each of the numbers.

Referring now to FIGS. 8 and 9, there is seen an alternate heaterconstruction designated generally by reference numeral 100. The heater100 includes a main manifold chamber 101 which is in fluid communicationwith a distribution conduit 102 extending along the major length of theheater. Extending transversely of the distribution conduit 102 are aplurality of manifold fuel distribution arms 103 and 104 of differentlengths, the shorter being the distribution arms 103- and the longerbeing the distribution arms 104. An air fuel mixture is delivered to themanifold chamber 101 by means of an inlet duct 106. By thus providingrelatively small volume distribution arms and feed conduit from the mainmanifold chamber 101 the amount of air fuel mixture which is capturedtherein at any given time is substantially reduced so that a moreeconomic and safe burner arrangement is provided.

The heater unit 100 is provided with a pair of brackets 107 and 108 formounting the heater to a road refinishing machine or to a tractor, asdesired. Therefore, the heater unit 100 can be used for repairinglimited areas of road surface as mentioned above.

Seen in FIG. v is a cross-section of a modified heater unit secured tothe top wall 109 which is of refractory material and is heated by meansof the deflected flame. This refractory-material also causes radiantheat. to be generated and directed downwardly toward the road surface toform a more efficient heating unit.

'A plurality of heaters 110 have a combustion chamber 111, partiallyembedded into the refractory wall 109, as best seen in FIG. 10, and afuel feed pipe 112 extending therefrom threadedly to engage a meteringorifice member 113 located within the distribution arm manifold portions103 and 104. In this instance a spark arrester safety screen 1 16 isinserted into the feed pipe 112 immediately downstream of the meteringorifice 113 so that inadvertent backfire into the manifold system isprevented.

A conical deflection member 117 is fastened to the radiant heatingelement 118 by a bolt 119 threadedly engaged therewith. The conicaldeflection member preferably is of high temperature refractory materialand fashioned to cause a change in direction of the flame emanating fromthe combustion chamber 111. The flame then passes laterally across theradiant heating element so that radiant heat is directed toward the roadsurface. This arrangement substantially minimizes the presence of aflame between the radiant heating element andthe road surface, whichflame would otherwise tend to insulate the road surface from the maximumheating by the radiant heat.

As mentioned above, there are two spaced apart heating structuresassociated with the road resurfacing apparatus 10 of FIG. 1, it beingunderstood that more heating units can be incorporated as desired. Alsoa single heating structure can be used on the back of a tractor or thelike to heat limited areas of road surface for small repairs. Whileseveral specific embodiments of the radiant heating structure of thisinvention are disclosed herein it will be understood that variations andmodifications thereof may be effected without departing from the spiritand scope of the novel concepts as defined by the appended claims.

The invention is claimed as follows:

1. Equipment for heating the upper strata of asphalt concrete pavement,or the like, comprising in combination: a chamber having chamber-formingwalls including a roof adapted to overlie an area of the'pavement to beheated by radiant heat, said chamber-forming walls including downwardlyextending peripheral side portions having lower edges thereof adapted tobe closely spaced to the pavement, heater means positioned within saidchamber for directing a flame toward the pavement, and radiant heatingelement means positioned within said chamber to be at all times betweenthe products of combustion from said heater means and the pavement beingheated, said radiant heating element means receiving the flame from saidheater means, and redirecting the flame laterally and converting suchflame heat to radiant heat, and exhaust manifold means in communicationwith said chamber at a point above said radiant heating element means toremove the products of combustion, whereby the pavement is heated to adepth greater than otherwise obtained by a direct flame from said heatermeans.

2. The equipment for heating the upper strata of asphalt concretepavement according to claim 1 wherein .said heating means comprises aplurality of discrete heating nozzles positioned within said chamber anddi- I rected toward the pavement, and wherein said radiant heatingelement means include a corresponding plurality of discrete radiantheating elements secured to the underside of each of said nozzles. I

3. The equipment for heating the upper strata of asphalt concretepavement according to claim 2 wherein said radiant heating elements areformed of a screenlike structure adapted to radiate energy of long redand infra-red wave lengths.

4'. The equipment for heating the upper strata of asphalt concretepavement according to claim 3 wherein said radiant heating elements areformed of screen-like structures of heat-and-oxidation-resistant nickelalloy.

5. The equipment for heating the upper strata of asphalt concretepavement according to claim 1 further including air blower, supply meansassociated with said heating means, said air blower supply meansincluding to redirect the flame from said heating element means radiallyoutwardly along the top surface of said radiant heating element means sothat maximum heating thereof is effected and no direct flame impingesupon the pavement being heated.

7. The equipment for heating the upper strata of asphalt concretepavement according to claim 1 further including a fuel distributingmanifold positioned about said chamber wherein said heating meansincludes a plurality of discrete heating elements each having anorificed end thereof inserted into said fuel distribution manifold, andfurther including adjustable air supply means connected to said fueldistributing manifold for admixing a variable supply of air with thefuel to be burned.

8. The equipment for heating the upper strata of asphalt concretepavement according to claim 7 further including preheating meanspositioned within said chamber adjacent said heating menas, saidpreheating means having an output end connected to said fueldistribution manifold for delivering thereto a quantity of preheatedfuel to be mixed with the air supply prior to delivery to said heatingmeans.

9. The equipment for heating the upper strata of asphalt concretepavement according to claim 7 wherein said fuel distribution manifold isof substantially the same size and configuration as said chamber, saidfuel distribution manifold being positioned above and closely spaced tosaid chamber.

10. Equipment for heating the upper strata of asphalt concrete pavement,or the like, comprising in combination: a heating chamber havingchamber-forming walls including a roof adapted to overlie and area ofthe pavement to be heated by radiant heat, said chamberforming wallsincluding downwardly extending peripheral side portions having loweredges thereof adapted to be closely spaced to the pavement, a fueldistribution manifold positioned over said heating chamber and closelyspaced thereto, said fuel distribution manifold having an air-fuelmixing chamber at the upper end thereof, a source of fuel connected tosaid air-fuel mixing chamber, a variable volume air supply connected tosaid air-fuel mixing chamber, a plurality of discrete heating nozzlespositioned within said heating chamber for directing a flame toward thepavement, said heating nozzles each having a short conduit portionextending from said heating chamber into said fuel disribution manifold,and radiant heating element means positioned within said chamber to beat all times between the products of combustion from said heatingnozzles and the pavement being heated, said radiant heating elementmeans receiving the flame from said heating nozzles and redirecting theflame radially outwardly across said radiant heating element means forconverting the flame heat to radiant heat, and exhaust manifold means incommunication with said chamber at a point above said radiant heatingelement means to remove the products of combustion.

11. The equipment for heating the upper strata of asphalt concretepavement according to claim 10 wherein each of said heating nozzlesincludes a cylindrical body connected to the bottom of each conduit, abaffle element positioned radially inwardly within said body to create aturbulent condition of the flame as it leaves the nozzle, a plurality ofradially outwardly and depending leg elements secured to saidcylindrical body, and means securing said radiant heating element meansto said legs.

12. The equipment for heating the upper strata of asphalt concretepavement according to claim 1 1 further including flame deflection meanssecured to said radiant heating element means and in registry beneathsaid body so that the flame therefrom will impinge upon said deflectorand be directed radially outwardly along said radiant heating elementmeans.

13. The equipment for heating the upper strata of asphalt concretepavement according to claim 10 further including fuel preheating meansarranged between the fuel supply and said air-fuel mixing chamber forpreheating the fuel mixture so that minimum expansion of gas occurs whenthe fuel mixture is burned.

14. Equipment for heating asphalt pavement or the like comprisingchamber means for closely overlying an area to be heated, heater meansassociated with said chamber means for directing a heating flame withinsaid chamber means and a radiant heating element mounted within thechamber means to be at all time between the products of combustion fromsaid heater means and the pavement being heated for receiving heat fromsaid flame and radiantly heating the pavement, and exhaust manifoldmeans in communication with said chamber means at a point above saidradiant heating element means to remove the products of combustiontherethrough.

15. In the equipment of claim 14 wherein said heating means is disposedfor directing flame downwardly toward pavement and said radiant heatingelement, and

' means for deflecting the flame along said radiant heating element andfor preventing direct impingement of the flame against said pavement.

16. In the equipment of claim 15 wherein said radiant heating element isa screen-like structure.

17. In the equipment of claim '16 including a plurality of said heatingmeans and radiant heating elements, 7

and mounting means for deflecting a flame and spaced in a predeterminedpattern within said chamber means.

18. In the equipment of claim 14, further including, fuel feed manifoldmeans having a main fuel input manifold section positioned over saidchamber means and occupying an area less than said chamber means, adistribution conduit connected to said fuel input manifold section andextending across at least one dimension of said chamber means on topthereof, and a plurality of hollow arms connected to and in the .fluidcommunication with said distribution conduit to feed air fuel mixture tosaid heater means assembled within said chamber means.

19. In the equipment of claim 18 wherein said heater means includes aplurality of discrete heating units each including a threaded pipethreadedly engaging a metering orifice secured to the interior of therespective associated hollow arms for receiving air fuel mixturetherefrom.

20. In the equipment of claim 19 further including a coiled screen,spark arrester element positioned within said pipe to prevent backfirefrom said heater units into said hollow arms.

21. The equipment for heating the upper strata of asphalt concretepavement according to claim 1, wherein said exhaust manifold meanspasses through said roof of said chamber.

1. Equipment for heating the upper strata of asphalt concrete pavement,or the like, comprising in combination: a chamber having chamber-formingwalls including a roof adapted to overlie an area of the pavement to beheated by radiant heat, said chamber-forming walls including downwardlyextending peripheral side portions having lower edges thereof adapted tobe closely spaced to the pavement, heater means positioned within saidchamber for directing a flame toward the pavement, and radiant heatingelement means positioned within said chamber to be at all times betweenthe products of combustion from said heater means and the pavement beingheated, said radiant heating element means receiving the flame from saidheater means, and redirecting the flame laterally and converting suchflame heat to radiant heat, and exhaust manifold means in communicationwith said chamber at a point above said radiant heating element means toremove the products of combustion, whereby the pavement is heated to adepth greater than otherwise obtained by a direct flame from said heatermeans.
 2. The equipment for heating the upper strata of asphalt concretepavement according to claim 1 wherein said heating means comprises aplurality of discrete heating nozzles positioned within said chamber anddirected toward the pavement, and wherein said radiant heating elementmeans include a corresponding plurality of discrete radiant heatingelements secured to the underside of each of said nozzles.
 3. Theequipment for heating the upper strata of asphalt concrete pavementaccording to claim 2 wherein said radiant heating elements are formed ofa screen-like structure adapted to radiate energy of long red andinfra-red wave lengths.
 4. The equipment for heating the upper stratA ofasphalt concrete pavement according to claim 3 wherein said radiantheating elements are formed of screen-like structures ofheat-and-oxidation-resistant nickel alloy.
 5. The equipment for heatingthe upper strata of asphalt concrete pavement according to claim 1further including air blower supply means associated with said heatingmeans, said air blower supply means including a variable air flow outputfor adjusting the turbulence of the flame produced by the heating means,whereby the pressure within said chamber is maintained substantiallybalanced with the atmospheric pressure externally of said chamber aboutthe closely spaced edges of said side walls.
 6. The equipment forheating the upper strata of asphalt concrete pavement according to claim1 further including deflector means positioned between said heatingmeans and said radiant heating element means to redirect the flame fromsaid heating element means radially outwardly along the top surface ofsaid radiant heating element means so that maximum heating thereof iseffected and no direct flame impinges upon the pavement being heated. 7.The equipment for heating the upper strata of asphalt concrete pavementaccording to claim 1 further including a fuel distributing manifoldpositioned about said chamber wherein said heating means includes aplurality of discrete heating elements each having an orificed endthereof inserted into said fuel distribution manifold, and furtherincluding adjustable air supply means connected to said fueldistributing manifold for admixing a variable supply of air with thefuel to be burned.
 8. The equipment for heating the upper strata ofasphalt concrete pavement according to claim 7 further includingpreheating means positioned within said chamber adjacent said heatingmenas, said preheating means having an output end connected to said fueldistribution manifold for delivering thereto a quantity of preheatedfuel to be mixed with the air supply prior to delivery to said heatingmeans.
 9. The equipment for heating the upper strata of asphalt concretepavement according to claim 7 wherein said fuel distribution manifold isof substantially the same size and configuration as said chamber, saidfuel distribution manifold being positioned above and closely spaced tosaid chamber.
 10. Equipment for heating the upper strata of asphaltconcrete pavement, or the like, comprising in combination: a heatingchamber having chamber-forming walls including a roof adapted to overlieand area of the pavement to be heated by radiant heat, saidchamber-forming walls including downwardly extending peripheral sideportions having lower edges thereof adapted to be closely spaced to thepavement, a fuel distribution manifold positioned over said heatingchamber and closely spaced thereto, said fuel distribution manifoldhaving an air-fuel mixing chamber at the upper end thereof, a source offuel connected to said air-fuel mixing chamber, a variable volume airsupply connected to said air-fuel mixing chamber, a plurality ofdiscrete heating nozzles positioned within said heating chamber fordirecting a flame toward the pavement, said heating nozzles each havinga short conduit portion extending from said heating chamber into saidfuel disribution manifold, and radiant heating element means positionedwithin said chamber to be at all times between the products ofcombustion from said heating nozzles and the pavement being heated, saidradiant heating element means receiving the flame from said heatingnozzles and redirecting the flame radially outwardly across said radiantheating element means for converting the flame heat to radiant heat, andexhaust manifold means in communication with said chamber at a pointabove said radiant heating element means to remove the products ofcombustion.
 11. The equipment for heating the upper strata of asphaltconcrete pavement according to claim 10 wherein each of said heatingnozzles includes a cylindrical body connected to the bottom of eachconduit, A baffle element positioned radially inwardly within said bodyto create a turbulent condition of the flame as it leaves the nozzle, aplurality of radially outwardly and depending leg elements secured tosaid cylindrical body, and means securing said radiant heating elementmeans to said legs.
 12. The equipment for heating the upper strata ofasphalt concrete pavement according to claim 11 further including flamedeflection means secured to said radiant heating element means and inregistry beneath said body so that the flame therefrom will impinge uponsaid deflector and be directed radially outwardly along said radiantheating element means.
 13. The equipment for heating the upper strata ofasphalt concrete pavement according to claim 10 further including fuelpreheating means arranged between the fuel supply and said air-fuelmixing chamber for preheating the fuel mixture so that minimum expansionof gas occurs when the fuel mixture is burned.
 14. Equipment for heatingasphalt pavement or the like comprising chamber means for closelyoverlying an area to be heated, heater means associated with saidchamber means for directing a heating flame within said chamber meansand a radiant heating element mounted within the chamber means to be atall time between the products of combustion from said heater means andthe pavement being heated for receiving heat from said flame andradiantly heating the pavement, and exhaust manifold means incommunication with said chamber means at a point above said radiantheating element means to remove the products of combustion therethrough.15. In the equipment of claim 14 wherein said heating means is disposedfor directing flame downwardly toward pavement and said radiant heatingelement, and means for deflecting the flame along said radiant heatingelement and for preventing direct impingement of the flame against saidpavement.
 16. In the equipment of claim 15 wherein said radiant heatingelement is a screen-like structure.
 17. In the equipment of claim 16including a plurality of said heating means and radiant heatingelements, and mounting means for deflecting a flame and spaced in apredetermined pattern within said chamber means.
 18. In the equipment ofclaim 14, further including, fuel feed manifold means having a main fuelinput manifold section positioned over said chamber means and occupyingan area less than said chamber means, a distribution conduit connectedto said fuel input manifold section and extending across at least onedimension of said chamber means on top thereof, and a plurality ofhollow arms connected to and in the fluid communication with saiddistribution conduit to feed air fuel mixture to said heater meansassembled within said chamber means.
 19. In the equipment of claim 18wherein said heater means includes a plurality of discrete heating unitseach including a threaded pipe threadedly engaging a metering orificesecured to the interior of the respective associated hollow arms forreceiving air fuel mixture therefrom.
 20. In the equipment of claim 19further including a coiled screen, spark arrester element positionedwithin said pipe to prevent backfire from said heater units into saidhollow arms.
 21. The equipment for heating the upper strata of asphaltconcrete pavement according to claim 1, wherein said exhaust manifoldmeans passes through said roof of said chamber.